With the aid of a computer-based anaesthetic record-keeping system, anaesthetics complicated by bronchospasm during anaesthesia at the Karolinska Hospital were retrieved. The incidence of bronchospasm was calculated in groups characterized by various variables. In total, 246 cases of bronchospasm in 156,064 anaesthetics were retrieved. This corresponds to one case in 634 anaesthetics or 1.7 per 1000 patients. High incidence figures were seen in the age group 0-9 years (4.0/1000) when the patients showed a respiratory infection (41.1/1000), a pathological preoperative ECG (24.3/1000), an obstructive lung disease (21.9/1000), were classified as belonging to ASA class III (23.8/1000), if a tracheal intubation was performed (9.1/1000) or a rectal anaesthesia (35.7/1000) was given. In the age group 50-69 years (1.8/1000), high incidence figures were seen when there was an airway obstruction (8.8/1000), an obstructive lung disease (7.7/1000), a previous myocardial infarction (5.4/1000), a bronchoscopy (7.6/1000) or a mediastinoscopy (7.8/1000) was performed. Most of the cases had no history of allergy or asthma recorded in the anaesthetic form. In this series the triggering factor more often seemed to be of mechanical origin. There were no intraoperative deaths.